Adversaries have developed sophisticated tools for hiding underground and in spaces below ground level and in buildings. They have further developed techniques that help them hide from density searches and infrared.
Previous work in this area position-adaptive radar includes Atindra K. Mitra and Krishna M. Pasala, “Low-Cost position-Adaptive Unmanned Aviation Vehicle (UAV) Radar Design with State-of-the-Art COTS Technology,” Radar Sensor Technology X, DSS 2004 and Atindra K. Mitra, “Leakage Signal Analysis for Position-Adaptive UAV Radar Applications,” Radar Sensor Technology XI, DSS 2005, both incorporated herein by reference. These articles have addressed topics such as short-range monostatic position-adaptive radar design for mini-unmanned aviation vehicle helicopter platforms as well as electromagnetic phenomenology and associated signal processing for position-adaptive radar. Some of these position-adaptive radar designs are based on state-of-the-art ultra-wideband impulse radar technology.
The present invention uses a plurality of platforms to transmit waveform signals with different sub-chirp intervals. At least a plurality of the sub-chirp intervals is received by a receiver or receiver means. The means for receiving the sub-chirp intervals may be any means known in the art such as digital receivers. The receiver is designed to receive the sub-chirp signals and process the sub-chirp signals over the entire chirp interval that is covered by all the transmitted sub-chirps. Alternatively, the receiving means may processes a plurality of the sub-chirp signals over a plurality of the chirp interval that is covered by a plurality of the transmitted sub-chirps.
Chirp and sub-chirp technology is different from ultrasonic imaging because spatially coded waveforms of radio and microwaves with sub-chirp technology provide a new capability for detecting directional multipath as opposed to traditional Radio Frequency (RF) and microwave imaging systems that rely on line-of-sight propagation. The present invention is non-acoustical and employs the data from multiple transmitters as received at a single receiver location.
Chirp and sub-chirp technology has several advantages over other sound imaging techniques in that spatially coded waveforms with sub-chirp technology provide an enhanced capability to detect critical directional information and characteristics of objects-of-interest that are embedded in remote cavities or channels such as caves or buildings.